Recycling of road surfacings

ABSTRACT

The present invention relates to a process for the production of roads, tracks, and other areas used by traffic, by producing a mixture comprising ground road surfacing, mineral material, and/or glass, a polymer reaction mixture and, if desired, further additions, and applying it to a substrate material, and hardening it. The present invention further relates to roads, tracks, and other areas used by traffic, obtainable by a process of this type.

The present invention relates to a process for the production of roads, tracks, and other areas used by traffic, by producing a mixture comprising ground road surfacing, mineral material, and/or glass, a polymer reaction mixture and, if desired, further additions, and applying it to a substrate material, and hardening it. The present invention further relates to roads, tracks, and other areas used by traffic, obtainable by a process of this type.

Further embodiments of the present invention are found in the claims, in the description, and in the examples. The abovementioned features of the subject matter of the invention, and the features that will be explained below, can of course be used not only in the respective stated combination but also in other combinations, without exceeding the scope of the invention.

Roads are mostly produced from asphalt, by applying a mineral mixture, mostly with bitumen as binder, if appropriate in a plurality of layers, to the substrate. Road surfacings using a plastic as binder are also known, for example as described in DE 19605990 and DE 19651749.

Bitumen-based roads usually have to be renewed after about 12 to 18 years, as a function of quality and loading, and after as little as from 6 to 7 years if the top layers have open pores. For this, the old asphalt is removed entirely or to some extent. Small amounts of the material removed can, if appropriate, be recycled with the same grain size distribution up to a level which is preferably 15% by weight. For this, the material must be conveyed to an asphalt mixing plant, where it is mixed at temperatures of about 180° C. with fresh bitumen and also with mineral material. The resultant asphalt is then in turn conveyed from the asphalt mixing plant to the installation site. This procedure causes severe environmental pollution, in particular by virtue of the truck traffic necessary for this purpose, and also by virtue of the high energy consumption in the asphalt mixing plant. A further factor is that asphalt which cannot be reused, the binder of which still comprises a proportion of tar, has to be discarded as special waste, because tar is toxic.

It was an object of the present invention to provide a process which can produce roads, tracks, and other areas used by traffic, and which reduces pollution of the environment.

The object of the invention is achieved via a process for the production of roads, tracks, and other areas used by traffic, by producing a mixture comprising ground road surfacing, mineral material, and/or glass, a polymer reaction mixture and, if desired, further additions, and applying it to a substrate material, and hardening it.

Roads, tracks, and other areas used by traffic are usually composed of a plurality of layers. These have at least one bound top layer at the surface, and also, if appropriate, further bound and unbound, deeper, layers. The bound deeper layers are usually what are known as the load-bearing layers, and the unbound deeper layers are usually base layers composed of rubble and gravel. The usual materials used as binders for the bound top layers and load-bearing layers are cement, plastic, or bitumen.

The process of the invention relates here to the production of bound layers. These can either be load-bearing layers or top layers. The main difference between the load-bearing layers and top layers is the average diameter of the mineral material used. The process of the invention preferably relates to the production of top layers. The substrate material used can be any desired material, examples being sand, earth, loam, concrete, stone. Substrate materials are preferably base layers and/or load-bearing layers.

According to the invention, ground road surfacing means either ground or broken top layers or else ground or broken load-bearing layers, and ground rubble layers or ground gravel layers. The ground road surfacing is preferably ground bound layers, in particular ground top layers. The binder for the ground bound layers here is preferably a binder based on polymers or based on bitumen, in particular based on bitumen. This particularly preferred variant utilizes not only the thermoplastic or viscoelastic properties of bitumen but also the high-temperatures of the polymer binder. The grain size distribution of the ground road surfacing here can be adjusted in a known manner by adapting the grinding conditions or removing undesired grain sizes. According to the invention, it is also possible to use pored-asphalt-based top layers as a base for ground road surfacing.

The mineral material used here can comprise any known mineral material. By way of example, sand or ground stone, known as broken material, can be used here, where sand has a mainly round surface and broken material has edges and fracture surfaces. It is particularly preferable that the mineral material used comprises a material which is mainly composed of broken material.

The glass used preferably comprises ground or broken glass. Broken glass here is preferably colored glass, permitting, for example, application of markings. Glass can be used here together with mineral material or instead of mineral material. It is preferable to use only mineral material, and no glass.

The grain size distribution of the mixture composed of ground road surfacing and of mineral material and/or glass is particularly preferably one based on the specifications encountered in bituminous road construction, being a function of the intended use, for example for load-bearing layers and top layers, examples being stone-filled mastic asphalt or drainable asphalt. The grain size distribution can be adjusted either via adjustment of the grain sizes of the ground road surfacing or else via use of mineral material with certain grain size distribution, or both. The ground road surfacing and the mineral material here can be mixed in any ratio by weight. The proportion of ground road surfacing is preferably smaller than 95% by weight, particularly preferably from 5 to 80% by weight, and in particular from 10 to 70% by weight, based on the total weight of the mixture composed of ground road surfacing and of mineral material.

A polymer reaction mixture here means a mixture capable of reacting to give a polymer. These mixtures encompass those comprising molecules which by way of example can react to give the polymer via chain-growth reactions, e.g. free-radical polymerization, or ionic polymerization, examples being unsaturated compounds, or molecules capable of entering into polycondensation reactions, examples being polyalcohols, or molecules capable of entering into polyaddition reactions, examples being polyols and polyisocyanates, or those such as epoxides. Polymer reaction mixtures of the invention are preferably liquid at 40° C.

The polymer reaction mixture preferably involves a mixture for the production of an epoxy resin or of a polyurethane. In particular, it involves a mixture for the production of a polyurethane, a polyurethane reaction mixture. The polymer reaction mixture here preferably comprises in essence no solvents.

The polymers obtained from a polymer reaction mixture are preferably compact, and this means that they comprise practically no pores. A feature of compact polymers, when compared with cellular polymers, is greater mechanical stability. Bubbles can occur within the polymer and are mostly not critical. However, they should be minimized as far as possible. It is moreover preferable that the resultant polymers are hydrophobic. This suppresses degradation of the polymers by water.

Polymer reaction mixtures of the invention preferably comprise compounds for improving adhesion to the recycling material and also to the mineral material. By way of example, these are hydroxy- or alkoxyaminosilane compounds of the general formula (I)

in which X are, independently of one another, OH, CH₃, O[CH₂]_(p)CH₃; Y is [CH₂]_(t), [(CH₂)_(r)NH(CH₂)_(s)]_(b), [(CH₂)_(r)NH(CH₂)_(s)NH(CH₂)_(z)]_(b); R, R′ is H, [CH₂]_(t)CH₃; t is 0-10; n is 1-3; p is 0-5; m is 4-n; r, s, b, and z are, independently of one another, 1-10.

The alkoxyaminosilane compound (I) is generally a trihydroxy-, dialkoxy- or trialkoxyaminosilane compound. Preferred alkoxy radicals X are methoxy and ethoxy. The amino group must be an amino group reactive toward isocyanate groups, i.e. a primary or secondary amino group. Preferred alkyl radicals R are hydrogen, methyl, and ethyl.

The alkoxyaminosilane compound (I) preferably involves a trihydroxyaminosilane compound or a trialkoxyaminosilane compound, where, in formula (I), X=OH or O[CH₂]_(p)CH₃, and p=0, 1.

It is further preferable that the alkoxyaminosilane compound (I) involves an alkoxydiaminosilane compound, where, in formula (I), Y=[CH₂]₁NH[CH₂]_(s), and r and s are identical or different, being 1 or 2. Examples are [CH₂]₃NH[CH₂]₂, [CH₂]₂NH[CH₂]₂, [CH₂]NH[CH₂], [CH₂]₃NH[CH₂]₃, [CH₂CH(CH₃)CH₂]NH[CH₂]₂ and [CH₂]₂NH[CH₂]₃.

The alkoxyaminosilane compound (I) in particular involves a trialkoxydiaminosilane compound, where, in formula (I), X=O[CH₂]_(p)CH₃, where p=0, 1, and Y=[CH₂]_(r)NH[CH₂]_(s), where r and s are identical or different, being 1 or 2.

Particularly preferred alkoxyaminosilane compounds (I) are 3-triethoxysilyipropylamine, N-(3-trihydroxysilylpropyl)ethylenediamine, N-(3-trimethoxysilylpropyl)ethylenediamine, and N-(3-methyldimethoxymethylsilyl-2-methylpropyl)ethylenediamine.

The polymer reaction mixture here generally comprises a concentration of from 0.01 to 10% by weight, preferably from 0.1 to 1% by weight, based on the total weight of the polymer reaction mixture, of the compounds for improving adhesion. The compound for improving adhesion here can also have reacted previously with further constituents of the polymer reaction mixture, for example by way of any OH group present.

For the purposes of this invention, a mixture for the production of an epoxy resin means a mixture which comprises compounds comprising epoxy groups, and comprises suitable hardeners. The mixtures here are capable, starting from the compounds comprising epoxy groups, of forming epoxy resins by way of said epoxy groups through polyaddition, using suitable hardeners. The invention uses the expression “a mixture for the production of an epoxy resin” when conversion in the reaction, based on the epoxy groups used for the production of the epoxy resin, is preferably smaller than 90%, particularly preferably smaller than 75%, and in particular smaller than 50%.

Compounds used comprising epoxy groups are preferably compounds which have at least two epoxy groups and which are liquid at room temperature. Mixtures of different compounds comprising epoxy groups can also be used here. It is preferable that said compounds are hydrophobic or that the mixtures comprise at least one compound which is hydrophobic and which comprises epoxy groups. Hydrophobic compounds of this type are by way of example obtained via a condensation reaction of bisphenol A or bisphenol F with epichlorohydrin. Said compounds can be used individually or in the form of a mixture.

In one embodiment, mixtures are used which are composed of above-mentioned hydrophobic compounds, comprising epoxy groups, with self-emulsifiable hydrophilic compounds, comprising epoxy groups. These hydrophilic compounds are obtained here via introduction of hydrophilic groups into the main chain of the compound comprising epoxy groups. Compounds of this type and processes for their production are disclosed by way of example in JP-A-7-206982 and JP-A-7-304853.

Hardeners used comprise compounds which catalyze the homopolymerization of the compounds comprising epoxy groups, or which react covalently with the epoxy groups or with the secondary hydroxy groups, examples being polyamines, polyaminoamides, ketimines, carboxylic anhydrides, and melamine-urea-phenol adducts and formaldehyde adducts. It is preferable to use ketimines, obtainable via reaction of a compound having a primary or secondary amino group, e.g. diethylenetriamine, triethylenetetramine, propylenediamine, or xylylenediamine, with a carbonyl compound, such as acetone, methyl ethyl ketone, or isobutyl methyl ketone, or to use alphatic, alicyclic, and aromatic polyamine compounds and polyamide compounds. Hardeners used with particular preference are ketimines or compatible mixtures comprising ketimines.

The ratio of reactive groups in the hardener to epoxy groups is preferably from 0.7:1 to 1.5:1, particularly preferably from 1.1:1 to 1.4:1.

During the production of the epoxy resins, it is also possible to add further additives, such as solvents, reactive diluents, fillers, and pigments, alongside the compounds comprising epoxy groups, and alongside the hardeners used. Additives of this type are known to the person skilled in the art.

A polyurethane reaction mixture is a mixture composed of compounds having isocyanate groups and compounds having groups reactive toward isocyanates, where the reaction conversion, based on the isocyanate groups used for the production of the polyurethane reaction mixture, is preferably smaller than 90%, particularly preferably smaller than 75%, and in particular smaller than 50%. The compounds having groups reactive toward isocyanates here comprise not only high-molecular-weight compounds, such as polyether- and polyesterols, but also low-molecular-weight compounds, such as glycerol, glycol, and also water. If the reaction conversion, based on the isocyanate group, is greater than 90%, the term polyurethane is used below. A polyurethane reaction mixture here can also comprise further reaction mixtures for the production of polymers. Examples of further reaction mixtures that can be used for the production of polymers are reaction mixtures for the production of epoxides, of acrylates, or of polyester resins. The proportion of further reaction mixtures for the production of polymers here is preferably less than 50% by weight, based on the total weight of the polyurethane reaction mixture. It is particularly preferable that the polyurethane reaction mixture comprises no further reaction mixtures for the production of polymers.

The polyurethane reaction mixture can involve what are known as moisture-curing systems. These comprise isocyanate prepolymers which form polyurethanes or polyureas via addition of water or via humidity, mainly by forming urea groups.

It is preferable to use what are known as two-component systems for the production of the polyurethane reaction mixture. For this, an isocyanate component comprising compounds having isocyanate groups, and a polyol component comprising compounds having groups reactive toward isocyanates are mixed in quantitative proportions such that the isocyanate index is in the range from 40 to 300, preferably from 60 to 200, and particularly preferably from 80 to 150.

For the purposes of the present invention, isocyanate index here means the stoichiometric ratio of isocyanate groups to groups reactive toward isocyanate, multiplied by 100. Groups reactive toward isocyanate here means any of the groups which are comprised in the reaction mixture and which are reactive toward isocyanate, and this includes chemical blowing agents, but not the isocyanate group itself.

The polyurethane reaction mixture is preferably obtained by mixing of a) isocyanates with b) relatively high-molecular-weight compounds having at least two hydrogen atoms reactive toward isocyanate, and also, if desired, c) chain extenders and/or crosslinking agents, d) catalysts, and e) other additives. Compounds particularly preferably used as components a) and b), and also, if desired, c) to e) are those which lead to a hydrophobic polyurethane reaction mixture and to a hydrophobic polyurethane.

Isocyanates a) that can be used are in principle any of the room-temperature-liquid isocyanates having at least two isocyanate groups. Aromatic isocyanates are preferably used, particularly preferably isomers of tolylene diisocyanate (TDI) and of diphenylmethane diisocyanate (MDI), in particular mixtures composed of MDI and of polyphenylene polymethylene polyisocyanates (crude MDI). The isocyanates can also have been modified, for example by incorporating isocyanurate groups and carbodiimide groups, and in particular by incorporating urethane groups. The last-mentioned compounds are produced via reaction of isocyanates with a substoichiometric amount of compounds having at least two active hydrogen atoms and are usually termed NCO prepolymers. Their NCO content is mostly in the range from 2 to 32% by weight. The isocyanates a) preferably comprise crude MDI, with resultant increase in the stability of the polyurethane obtained.

In applications of the inventive process where high colorfastness is important, it is preferable to use mixtures comprising aliphatic isocyanates and aromatic isocyanates. It is particularly preferable to use exclusively aliphatic isocyanates. In one particular embodiment, an overlayer composed of polyurethane based on an aliphatic isocyanate can be used, in order to protect the top layer based on aromatic isocyanate from yellowing. The overlayer here can also comprise mineral material. Preferred representative aliphatic isocyanates are hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Because the aliphatic isocyanates have high volatility, they are mostly used in the form of their reaction products, in particular in the form of biurets, allophanates, uretonimines, or isocyanurates.

The isocyanates a) can also be used in the form of their prepolymers. For this, the isocyanates a) are reacted in a known manner in excess with compounds reactive toward isocyanate, for example with the relatively high-molecular-weight compounds listed under b), having at least 2 groups reactive toward isocyanate, to give prepolymers.

The relatively high-molecular-weight compounds b) used, having at least two hydrogen atoms reactive toward isocyanate preferably comprise compounds which have, as group reactive toward isocyanate, hydroxy groups or amino groups. Amino groups as groups reactive toward isocyanates lead to formation of urea groups, which in turn harden to give a polyurethane which is mostly brittle, but which has very good hydrolysis resistance and chemicals resistance. The relatively high-molecular-weight compounds b) used, having at least two hydrogen atoms reactive toward isocyanate preferably comprise polyhydric alcohols, since these generally react more slowly than compounds having amino groups and thus permit longer processing times. Given appropriate high molar masses, for example greater than 1500 g/mol, the use of polyhydric alcohols moreover gives a relatively elastic material.

The relatively high-molecular-weight, polyhydric alcohols used can by way of example comprise polyethers or polyesters. Further compounds having at least two hydrogen atoms reactive toward isocyanate groups can be used together with the compounds mentioned.

Because of their high hydrolysis resistance, polyether alcohols are preferred as relatively high-molecular-weight compounds b) having at least two hydrogen atoms reactive toward isocyanate. These are produced by conventional and known processes, mostly via an addition reaction of alkylene oxides onto H-functional starter substances. The functionality of the polyether alcohols used concomitantly is preferably at least 2, their hydroxy number being at least 10 mg KOH/g, preferably at least 15 mg KOH/g, in particular in the range from 20 to 600 mg KOH/g. They are produced in a conventional manner via reaction of at least difunctional starter substances with alkylene oxides. Starter substances used can preferably comprise alcohols having at least two hydroxy groups in the molecule, examples being propylene glycol, monoethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol. Starter substances of relatively high functionality can preferably be glycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose. Alkylene oxides used preferably comprise ethylene oxide and propylene oxide, in particular propylene oxide.

The reaction mixtures of the invention preferably comprise compounds having hydrophobic groups. These particularly preferably involve hydroxy-functionalized compounds having hydrophobic groups. These compounds having hydrophobic groups have hydrocarbon groups preferably having more than 6, particularly preferably more than 8 and less than 200, and in particular more than 10 and less than 100, carbon atoms. The compounds having hydrophobic groups can be used as a separate component or as a constituent of one of components a) to e), for the production of the reaction mixture. The hydroxy-functionalized hydrophobic compounds preferably involve compounds which comply with the definition of the relatively high-molecular-weight compounds b) having at least two hydrogen atoms reactive toward isocyanates. Component b) here can comprise hydroxy-functionalized hydrophobic compounds or can preferably be composed thereof.

The hydroxy-functionalized hydrophobic compound used preferably comprises a hydroxy-functionalized compound known from oleochemistry, or a polyol known from oleochemistry.

A number of hydroxy-functional compounds that can be used are known in oleochemistry. Examples are castor oil, oils modified using hydroxy groups, e.g. grapeseed oil, black cumin oil, pumpkin seed oil, borage seed oil, soybean oil, wheatgerm oil, rapeseed oil, sunflower oil, peanut oil, apricot seed oil, pistachio oil, almond oil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil, sesame oil, hazelnut oil, evening primrose oil, wild rose oil, hemp oil, thistle oil, walnut oil, fatty acid esters modified using hydroxy groups and based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, or cervonic acid. It is preferable here to use castor oil and its reaction products with alkylene oxides or with ketone-formaldehyde resins. The last-named compounds are marketed by way of example by Bayer AG as Desmophen® 1150.

Another group of polyols which are known in oleochemistry and whose use is preferred can be obtained via ring-opening of epoxidized fatty acid esters with simultaneous reaction with alcohols and, if need be, subsequent further transesterification reactions. Incorporation of hydroxy groups into oils and fats occurs primarily via epoxidization of the olefinic double bond comprised in these products, followed by reaction of the resultant epoxy groups with a mono- or polyhydric alcohol. The product here of the epoxy ring is a hydroxy group or, in the case of polyhydric alcohols, a structure having a relatively high number of OH groups. Since oils and fats are mostly glycerol esters, parallel transesterification reactions proceed with the abovementioned reactions. The molar mass of the resultant compounds is preferably in the range from 500 to 1500 g/mol. These products are supplied by way of example by Henkel.

In one particularly preferred embodiment of the inventive process, the relatively high-molecular-weight compound b) having at least two hydrogen atoms reactive toward isocyanate comprises at least one polyol known in oleochemistry and at least one phenol-modified aromatic hydrocarbon resin, in particular one indene-coumarone resin. Polyurethane reaction mixtures based on said component b) have a level of hydrophobic properties which is sufficiently high that in principle they can even be hardened under water, or installed during rainfall.

The phenol-modified aromatic hydrocarbon resin used having a terminal phenol group preferably comprises phenol-modified indene-coumarone resins, and particularly preferably industrial mixtures of aromatic hydrocarbon resins. These products are commercially available and are supplied by way of example by Rütgers VFT AG as NOVARES®.

The OH content of the phenol-modified aromatic hydrocarbon resins, in particular the phenol-modified indene-coumarone resins, is mostly from 0.5 to 5.0% by weight.

The polyol known from oleochemistry and the phenol-modified aromatic hydrocarbon resin, in particular the indene-coumarone resin, are preferably used in a ratio by weight of from 100:1 to 100:50.

Production of an inventive polyurethane reaction mixture can use a chain extender c). However, the chain extender c) can also be omitted here. However, the addition of chain extenders, crosslinking agents, or else, if desired, a mixture of these can prove successful for modification of mechanical properties, e.g. hardness.

If low-molecular-weight chain extenders and/or crosslinking agents c) are used, the production of polyurethanes can use known chain extenders. These are preferably low-molecular-weight compounds having groups reactive toward isocyanates whose molar mass is from 62 to 400 g/mol, examples being glycerol, trimethylolpropane, known glycol derivatives, butanediol, and diamines. Other possible low-molecular-weight chain extenders and/or crosslinking agents are given by way of example in “Kunststoffhandbuch, Band 7, Polyurethane” [Plastics Handbook, volume 7, Polyurethanes], Carl Hanser Verlag, 3rd edition 1993, chapter 3.2 and 3.3.2.

The polyurethanes used can in principle be produced without the presence of catalysts d). Catalysts d) can be used concomitantly to improve hardening. The catalysts d) selected should preferably be those that maximize reaction time. It is thus possible that the polyurethane reaction mixture remains liquid for a long period. These catalysts are known to the person skilled in the art. It is also possible in principle, as described, to work entirely without catalyst.

Other conventional constituents can be added to the polyurethane reaction mixture, examples being conventional additives e). These comprise by way of example conventional fillers. The fillers used are preferably the conventional, organic and inorganic fillers, reinforcing agents, and weighting agents known per se. Individual examples that may be mentioned are: inorganic fillers, such as silicatic minerals, e.g. phyllosilicates, such as antigorite, serpentine, hornblendes, amphiboles, chrysotile, metal oxides, such as kaolin, aluminum oxides, titanium oxides, and iron oxides, metal salts, such as chalk, barite, and inorganic pigments, such as cadmium sulfide, zinc sulfide, and also glass. It is preferable to use kaolin (China clay), aluminum silicate, and coprecipitates composed of barium sulfate and aluminum silicate, and also natural and synthetic fibrous minerals, such as wollastonite, metal fibers of various lengths, and in particular glass fibers of various lengths, which may, if desired, have been coated with a size. Examples of organic fillers that can be used are: carbon black, melamine, rosin, cyclopentadienyl resins, and graft polymers, and also cellulose fibers, polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, polyester fibers based on aromatic and/or aliphatic dicarboxylic esters, and in particular carbon fibers.

If the abovementioned inorganic fillers are used as additives e), their mineral substance constitution preferably differs from that of the mineral material, and they are ignored when determining the grain size distribution of the mineral material.

The inorganic and organic fillers can be used individually or in the form of a mixture, and their amounts comprised in the reaction mixture are preferably from 0.5 to 50% by weight, particularly preferably from 1 to 40% by weight, based on the weight of components a) to e).

The polyurethane reaction mixture should also comprise dryers, such as zeolites. These are preferably added, prior to production of the inventive reaction mixture, to the compounds b) having at least two hydrogen atoms reactive toward isocyanate, or to the component which comprises the compounds b) having at least two hydrogen atoms reactive toward isocyanate. Addition of the dryers avoids any increase in the concentration of water in the components or in the reaction mixture, and thus avoids formation of foamed polyurethane. Additions preferred for water adsorption are aluminosilicates, selected from the group of the sodium aluminosilicates, potassium aluminosilicates, calcium aluminosilicates, cesium aluminosilicates, barium aluminosilicates, magnesium aluminosilicates, strontium aluminosilicates, sodium aluminophosphates, potassium aluminophosphates, calcium aluminophosphates, and mixtures thereof. It is particularly preferable to use mixtures of sodium aluminosilicates, potassium aluminosilicates, and calcium aluminosilicates in castor oil as carrier substance.

To improve the long-term stability of the inventive top layers, it is moreover advantageous to add agents to counter attack by microorganisms. Addition of UV stabilizers is also advantageous, in order to avoid embrittlement of the moldings. These additives are known, and examples are given in “Kunststoffhandbuch, Band 7, Polyurethane” [Plastics Handbook, volume 7, Polyurethanes], Carl Hanser Verlag, 3rd edition 1993, chapter 3.4.

It is preferable that the components c), d), and e) are added to the compounds having at least two hydrogen atoms reactive toward isocyanate groups. This blend is often referred to in industry as polyol component.

The ratio in which the isocyanates are combined with the compounds having at least two hydrogen atoms reactive toward isocyanate groups should preferably be such that a stoichiometric excess of isocyanate groups is present.

In one preferred embodiment of the invention, polyurethane reaction mixtures are used which lead to hydrophobic, substantially compact polyurethanes. A polyurethane is termed compact polyurethane if it is substantially free from gas inclusions. The density of a compact polyurethane is preferably greater than 0.8 g/cm³, particularly preferably greater than 0.9 g/cm³, and in particular greater than 1.0 g/cm³.

Examples of materials that can be used as further additions are those which inhibit run-off of the binder from the mineral material. Examples of additions of this type that can be added are organic fibers, such as cellulose fibers. It is moreover possible to add polymers which are nowadays used in the bitumen-based systems used. These are especially neoprenes, styrene-butadiene-styrene, block copolymers, or a mixture of these, or else any of the other known rubbers or a mixture of these. The additions can either be added directly to the mineral mixture in the form of powder or granules, or else can be dispersed in one of the polyurethane components.

There is no restriction on the production of mixtures of the invention, comprising ground road surfacing, mineral material, and a polymer reaction mixture, and also, if used, further additions. They can by way of example be produced in mixers into which the ground road surfacing and the mineral material is introduced, and the starting components for the production of the polyurethane reaction mixture are introduced, for example by spraying. Additions to be added here, if desired, are preferably added to the mixture at the respective advantageous juncture. By way of example, therefore, these may be in solution or dispersion in one of the components of the reaction mixture, for example in one of components a) to e), and may be added with these to the mixture. The additions can also be separately added to the mixture. By way of example, cellulose fibers can be added at a juncture such that these are present in homogeneous dispersion in the mixture for the production of top layers, but are not irreversibly damaged by the mixing procedure. The inventive mixture here can by way of example be produced by the process described in DE 196 32 638. It is likewise possible, for example, to begin by producing the polyurethane reaction mixture and then to mix this with the mineral material and, if used, with the further additions. In another embodiment, the mineral material can, if desired, first be mixed with some of the components of the reaction mixture, for example with components b) and, if present, c) to e), and then the components not yet present, for example component a), can be added in a mixer. The mixture of the invention, comprising ground road surfacing, can be produced by a mobile method at the installation site. Transport to a central plant is not necessary.

The hydrophobic polyurethane reaction mixtures whose use is preferred feature particularly good processability. By way of example, said polyurethane reaction mixtures, and the polyurethanes obtained therefrom, feature particularly good adhesion. Because of the hydrophobic nature of the system, the polyurethane reaction mixture hardens despite the presence of water, e.g. rain, to give a practically compact product.

When the mixture of the invention is applied to the substrate material, it is not necessary that the substrate material is dry. Surprisingly, even when substrate material is wet, good adhesion is obtained between the load-bearing layer or the top layer and the substrate material.

The mixture of the invention here preferably comprises from 1 to 20% by weight, particularly preferably from 2 to 15% by weight, and in particular from 4 to 10% by weight, of polymer reaction mixture, based on the total weight of the mixture of the invention, comprising ground road surfacing, mineral material, and a polymer reaction mixture, and also, if desired, further additions.

The bond between mineral material and binder of the invention is very strong. Furthermore, particularly if hydroxy-functional compounds having hydrophobic groups are used, there is practically no hydrolytic degradation of the polyurethanes, and the durability of the top layers produced by the process of the invention is therefore very high. Top layers of the invention have particularly good load-bearing properties and are therefore suitable for all roads, tracks, and areas used by traffic, particularly for runways and for roads subject to relatively high loads in construction class V to I, particular III to I, and runways, where roads of construction class V are access roads, and roads of construction class I are motorways and highways. The mineral material used here preferably comprises the materials recommended for the respective construction class.

Surprisingly, and particularly when hydrophobic reaction mixtures are used, there is very little frost damage. A further advantage of top layers of the invention is low repair cost. It is sufficient, for example, that the mixture for the production of a top layer is produced, without heating, in small amounts in situ, and is applied to the damaged site and compacted. Furthermore, the mechanical properties of the top layers of the invention do not change over a period of a number of years. A further advantage of top layers of the invention is improved wet slip resistance, in particular in the case of top layers with high polyurethane content in comparison with top layers with high bitumen content.

It is preferable that the mixture comprising ground road surfacing, mineral material, and a polymer reaction mixture, and also, if desired, further additions is compacted after application to a substrate material. The intensity of compaction here depends on the desired application, by way of example, only a little compaction is used for the production of drainable asphalt, which can dissipate moisture, but a higher degree of compaction is used for the production of asphalt that can withstand high loadings. The degree of compaction needed also depends on the composition of the rock.

The process of the invention is preferably used for the renovation of roads. The ground road surfacing here is preferably obtained directly at the usage location by surface grinding to remove material from the road requiring renovation. The material obtained by the grinding process is preferably broken, ground, and/or sieved, in order to obtain a preferred grain size distribution. This recycling material is mixed with binder and with further mineral material and preferably reinstalled onto the road in situ, as load-bearing layer or top layer. For this, the appropriate substrate is preferably pretreated with familiar adhesion-promoter systems, for example with polyurethane-based spray adhesives. This serves to give an even greater improvement in the adhesion between the layers and to compensate any stresses arising, caused by high loading, for example heavy traffic load or caused by differences in coefficients of thermal expansion between substrate and load-bearing layer or top layer. The materials here are installed using equipment conventional in road construction. The installation equipment used here preferably has an antiadhesive coating, or has been wetted with a, preferably biologically based, release agent. It is preferable that the top layer installed is then provided with a coating of scattered fine-grain mineral material (e.g. sand), in order to give an even greater improvement in the good wet slip properties.

In comparison with the conventional process in which the new asphalt is obtained only in stationary asphalt plants, the process of the invention can save time and energy, by omitting the truck transport which is otherwise needed. A further feature of inventive tracks, roads, and areas used by traffic is very high durability, in particular when subject to frost-thaw cycles, and high elasticity, and exceptionally high strength. Top layers of the invention thus combine the favorable properties of bitumen-based top layers with top layers based on polymer reaction mixtures, e.g. polyurethanes or epoxides.

The invention is illustrated by the example below:

Polyurethane Reaction Mixture 1:

100 parts by weight of the polyol component of the Elastan 6551/101 system and 50 parts by weight of IsoPMDI 92140, a formulation comprising diphenylmethane diisocyanate (MDI) were mixed with one another.

10 parts by weight of polyurethane reaction mixture 1 are mixed with 90 parts by weight of a mixture composed of 90 parts by weight of mineral mixture (grain size 2/5, Piesberger) and with 10 parts by weight of a broken bitumen-based standard recycling material from an asphalt top layer, charged to a mold of dimensions 100×100×100 mm, compacted using 8.5 N/mm², and hardened.

The compressive strength of the resulting specimen was determined after more than 24 hours of storage, being 7.0 N/mm². This value shows that it is possible to produce top layers from this type of material. 

1. A process for producing a road, a track, or a different area bearing traffic, the process comprising: producing a first mixture comprising ground road surfacing, at least one selected from the group consisting of a mineral material and glass, a polymer reaction mixture, and optionally, at least one further addition; (ii) applying the first mixture to a substrate material; and (iii) hardening the first mixture.
 2. The process of claim 1, wherein the polymer reaction mixture is a mixture for producing a polyurethane.
 3. The process of claim 2, wherein the polymer reaction mixture comprises a compound which improves adhesion.
 4. The process of claim 1, wherein the polymer reaction mixture is obtained via mixing a) at least one isocyanate with b) at least one compound having at least two hydrogen atoms reactive toward isocyanate, c) at least one selected from the group consisting of a chain extender and a crosslinking agent, d) optionally, at least one catalyst, and e) optionally, at least one further additive.
 5. The process of claim 1, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 6. The process of claim 1, wherein a proportion of ground road surfacing is smaller than 95% by weight, based on a total weight of a mixture composed of ground road surfacing and mineral material in the first mixture.
 7. A top layer or load-bearing layer obtained by the process of claim 1, wherein the top layer or load-bearing layer is suitable for a road, a track, or a different area bearing traffic.
 8. The process of claim 2, wherein the polymer reaction mixture is obtained via mixing a) at least one isocyanate with b) at least one compound having at least two hydrogen atoms reactive toward isocyanate, c) at least one selected from the group consisting of a chain extender and a crosslinking agent, d) optionally, at least one catalyst, and e) optionally, at least one further additive.
 9. The process of claim 3, wherein the polymer reaction mixture is obtained via mixing a) at least one isocyanate with b) at least one compound having at least two hydrogen atoms reactive toward isocyanate, c) at least one selected from the group consisting of a chain extender and a crosslinking agent, d) optionally, at least one catalyst, and e) optionally, at least one further additive.
 10. The process of claim 2, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 11. The process of claim 3, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 12. The process of claim 4, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 13. The process of claim 8, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 14. The process of claim 9, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 15. The process of claim 1, wherein the polymer reaction mixture is a mixture for producing an epoxy resin.
 16. The process of claim 15, wherein the polymer reaction mixture comprises a compound which improves adhesion.
 17. The process of claim 15, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 18. The process of claim 16, wherein a proportion of the polymer reaction mixture is from 1 to 20% by weight, based on a total weight of the first mixture.
 19. The process of claim 15, wherein a proportion of ground road surfacing is smaller than 95% by weight, based on a total weight of the mixture composed of ground road surfacing and mineral material.
 20. A top layer or load-bearing layer obtained by the process of claim 15, wherein the top layer or load-bearing layer is suitable for a road, a track, or a different area bearing traffic. 